1. Field of the Invention
The present invention relates to a magnetic head employed in a magnetic recording device such as a magnetic disk drive, a magnetic tape recorder, etc., and a method of manufacturing the same.
2. Description of the Prior Art
As a magnetic head employed in a magnetic recording device such as a magnetic disk drive, a magnetic tape recorder, etc., there are an inductive type recording/reproducing head and a composite magnetic head which is equipped with both an inductive type recording head and a magnetoresistive reproducing head.
In recent years, with the higher density in the magnetic disk drive, etc., higher performance of the magnetic head has been requested. To provide a magnetic head which satisfy such a request, there has been much intrest in the MR head which does not depend upon the speed of the magnetic recording medium, which can be installed into the small disk drive, and can output high output.
In order to realize the high recording density in such magnetic head, both the linear recording density and the track density of the magnetic recording medium must be improved. Correspondingly, there is demand for a magnetic head which has a narrower core width, can record up to the high frequency, and has less of the side fringing of recording or ooze. "Side fringing of recording" means a phenomenon that a recording magnetic field is spread out along the track width direction in writing to exert an influence upon a track adjacent to the object track.
In the thin film magnetic head such as a head into which an MR head is installed, a magnetic head which is called a composite head has been well known. The composite head is formed by laminating a multi-layered reproducing head RE which reads magnetic information from a magnetic recording medium, and a multi-layered recording head WR which writes information magnetically onto the magnetic recording medium in the layer laminating direction.
A boundary member between the reproducing head RE and the recording head WR, i.e. one layer of a pair of magnetic shielding layers of the reproducing head RE positioned on the recording head side (referred to as "upper reproducing magnetic shielding layer" or simply "upper magnetic shielding layer" hereinafter) is used commonly to one layer of a pair of magnetic poles of the recording head WR positioned on the recording head side (referred to as "lower recording magnetic pole" or simply "lower magnetic pole" hereinafter). Therefore, certain constraints are imposed upon a shape of the layer and a side surface (ABS (Air Bearing Surface) or floating surface) which faces the magnetic recording medium, of the lower magnetic pole of the recording head WR is formed inevitably wider than the recording track width of the magnetic recording medium. For this reason, the recording magnetic field generated from the lower magnetic pole in writing operation is spread widely in the track direction of the recording medium. As a result, it is difficult to improve the recording density by narrowing the track width to reduce a track pitch.
The lower magnetic pole and the upper magnetic pole are connected to each other in a central area of a spiral recording coil 12. The recording magnetic field is generated between the ABS of the lower magnetic pole and the ABS of the upper magnetic pole. In order to improve the recording density, it is desired that the ABS of the upper magnetic pole be shaped as minute as possible and thus the side fringing of recording must be reduced.
(Problems to be overcome by the Invention)
In the recording head, the magnetic field intensity applied to the recording medium is normally set about two times the coercive force Hc of the recording medium. The coercive force Hc of the recent recording medium is approximately 2500 Oe (Oersted). Hence, an object of the present invention is that the magnetic head have a recording magnetic field of about 5000 Oe.
A second object of the present invention is to have the core width of the upper recording magnetic pole (longitudinal dimension of the ABS) of less than 1 .mu.m.
However, the upper recording magnetic pole is formed the interlayer insulating layer formed on the lower recording magnetic pole. Since the recording coil to be positioned above the lower recording magnetic pole is buried in the interlayer insulating layer, such interlayer insulating layer has a large step (high step) on its surface. As shown in FIG. 1A, if liquid resist is coated on the interlayer insulating layer 111 having the high step to form the upper magnetic pole, the resist 115 has such a tendency, because of flowability of resist, that the film thickness becomes relatively thin on the high step portion (flat portion) but the film thickness becomes relatively thick on the low step portion (step bottom portion) because of stagnant resist.
Therefore, in forming the upper magnetic pole, the upper magnetic pole must be plated on the surface of the interlayer insulating layer 111 having the high step, then patterned, and the like. In order to form the upper magnetic pole of a predetermined film thickness, about 6 .mu.m is needed as the film thickness of the resist on the flat portion. In this case, the film thickness of the resist on the step bottom becomes about 10 .mu.m.
It is very difficult to accomplish the target core width of 1 .mu.m on the ABS of the upper magnetic pole by using the resist having the film thickness of more than 10 .mu.m.
As the countermeasure to overcome the problem, the applicant of this application has proposed previously the technology, as disclosed in Japanese Patent Application No.9-109845 filed on Apr. 25, 1997 in Japan (which application has not been laid open to public at the application date of this Japanese application), that the upper recording electrode is partially trimmed by using the focused ion beam (FIB) method.
The technology disclosed in this Japanese Patent Application No.9-109845 document is that, in steps of manufacturing the composite magnetic head, the upper recording electrode is locally trimmed and shaped from the ABS side by using the focused ion beam method to narrow the core width before or after it is cut out into the slider at the final stage.
FIG. 1B is a view showing trimming of the upper magnetic pole by using the focused ion beam method. As schematically shown in FIG. 1B, in the magnetic head in which the upper magnetic pole is formed, the upper magnetic pole 116 covers partially the spiral recording coil 112. The upper magnetic pole 116 has an elongated (i.e. long and narrow) pole 16a being directed to the recording medium.
FIG. 1C is an enlarged view showing trimming of elongated pole 116a by using the focused ion beam method. More particularly, after the upper magnetic pole 116 is patterned, both sides of the elongated pole contacting the gap layer in the upper magnetic pole 116 and the lower magnetic pole located below and around the elongated pole are trimmed by irradiating the focused ion beam. According to this trimming process, the elongated pole width 116a of the upper magnetic pole 116 is shaped into a desired shape and at the same time grooves or concave portions are formed on the upper portion of the lower magnetic pole located below and on both sides of the elongated pole.
FIG. 2 is a view showing a focused ion beam equipment. This equipment comprises a pattern drawing portion which includes an ion source, a lens system, a stage, etc., and a control and data processing portion. Since the ion beam has a good straight propagation property, the focused ion beam method has a feature to enable very fine pattern formation. In addition, the fine patterns with a high aspect ratio can be formed.
Therefore, if the focused ion beam method is employed, the elongated pole 116a can be shaped into desired fine patterns by the trimming process. If the upper magnetic pole with the elongated pole which is shaped into such desired fine patterns is employed, spread of the recording magnetic field generated between the upper magnetic pole and the lower magnetic pole in the track width direction can be suppressed to the lowest minimum. As a result, the magnetic head having such upper magnetic pole can record information onto the magnetic recording medium having the high track density.
Nevertheless, executing the trimming process of the magnetic pole by using the focused ion beam method is very poor in productivity at the existing state. The focused ion beam method can be executed by the FIB equipment shown in FIG. 2. In order to trim the core width of the shaped elongated pole within 1 .mu.m, the ion beam is focused to the predetermined positions on both sides of the elongated pole every head and then the pattern drawing area is set to effect the trimming operation.
Since a plurality of heads are formed on the substrate, plenty of time is needed to repeat the steps by the number of heads. For example, if a processing time per head is set to about 10 seconds, one day or more (27.7 times) is consumed to process a sheet of wafer since about 10,000 heads are incorporated in the wafer of five(5)-inch in diameter which is relatively small in size.
In order to utilize the magnetic head in actual production, the processing time must be shortened considerably and also a large number of FIB equipments must be installed, but they are not practical solutions. Therefore, a new technology which can be replaced with the magnetic head manufacturing method employing the focused ion beam is needed.
Furthermore, it is more important that the above technology in Japanese Patent Application No.9-109845 document has disclosed the partial trimming process of the upper magnetic pole and the lower magnetic pole, but it is silent on the trimmed range, i.e., the trimmed shape which provides good influence on characteristics of the magnetic head.
Therefore, it is an object of the present invention to provide a novel magnetic head in light of the above problems.
It is another object of the present invention to provide a magnetic head having a narrow core width suitable for high density recording.
It is still another object of the present invention to provide a method of manufacturing a new magnetic head.
It is yet still another object of the present invention to provide a magnetic head having a narrow core width suitable for high density recording.